Catalyst system comprising a mixture of catalyst components for producing a polyolefin blend

ABSTRACT

Provided is a catalyst system for producing a polyolefin blend, which catalyst system comprises a mixture including the following catalyst components: i) a catalyst component A capable of producing an isotactic olefin polymer, and/or a catalyst component A′ capable of producing a polymer comprising an isotactic polyolefin block; and ii) a catalyst component B capable of producing a syndiotactic polyolefin, and/or a catalyst component B′ capable of producing a polymer comprising a syndiotactic polyolefin block; wherein each of the components in the catalyst system is distinct from the other components in the catalyst system.

The present invention relates to a catalyst system for use in preparingisotactic polyolefin/syndiotactic polyolefin blends, especiallyisotactic polypropylene/syndiotactic polypropylene (iPP/sPP) blends. Theinvention further relates to a catalyst system comprising metallocenecatalyst components and a process for producing iPP/sPP blends using thecatalyst system.

Olefins having 3 or more carbon atoms can be polymerised to produce apolymer with an isotactic stereochemical configuration. For example, inthe polymerisation of propylene to form polypropylene, the isotacticstructure is typically described as having methyl groups attached to thetertiary carbon atoms of successive monomeric units on the same side ofa hypothetical plane through the main chain of the polymer. This can bedescribed using a three dimensional stereochemical representation andthe corresponding Fischer projection formula as follows:

Another way of describing the structure is through the use of NMRspectroscopy. Bovey's NMR nomenclature for an isotactic pentad is “mmmm”with each “m” representing a “meso” diad or successive methyl groups onthe same side in the plane.

In contrast to the isotactic structure, syndiotactic polymers are thosein which the methyl groups attached to the tertiary carbon atoms ofsuccessive monomeric units in the chain lie on alternate sides of theplane of the polymer. The structure of a syndiotactic polymer isdescribed as follows using a three dimensional stereochemicalrepresentation and the corresponding Fischer projection formula:

In NMR nomenclature, a syndiotactic pentad is described as “rrrr” inwhich “r” represents a “racemic” diad with successive methyl groups onalternate sides of the plane.

In contrast to isotactic and syndiotactic polymers, an atactic polymerexhibits no regular order of repeating unit. Unlike syndiotactic orisotactic polymers, an atactic polymer is not crystalline and formsessentially a waxy product.

It is desirable to form blends of isotactic and syndiotacticpolyolefins, in particular blends of iPP and sPP. For instance, sPP isgenerally sticky, which reduces its processibility. This stickiness canbe reduced by blending sPP with iPP. In addition, sPP gives hightransparency and flexibility in injection blow moulding and injectionmoulding, whilst iPP gives improved processibility and fastersolidification. These advantageous properties can be optimised byblending the two polymers.

Moreover, the softness of polypropylene fibres can be improved byincorporating sPP in iPP, whilst the thermal bonding properties ofnon-woven fibres can be improved also by incorporating sPP in iPP. Byblending a small quantity of sPP with iPP the modulus of polypropylenefilms can be reduced thus forming films that are less stiff, whilstsimultaneously improving the heat shrink, tear resistance and impactresistance properties of the films.

The low crystallisation rate of sPP can be problematic, when processingsPP in a melt. However, the crystallisation rate of iPP is much greaterthat that of sPP. By incorporating some iPP in sPP, it is possible toincrease the crystallisation rate of sPP in the melt mixture, since asthe melt cools, iPP crystallises relatively quickly and serves to seedthe crystallisation of sPP. Thus, for this additional reason, it isdesirable to form blends of iPP and sPP.

In order to take advantage of the favourable properties of bothisotactic and syndiotactic polyolefins, it is known to prepare aphysical blend of such polyolefins. However, the properties of the aboveknown physical blends still fall short of the properties which should beachievable from homogeneous reactor blends. This is because polyolefinsare generally resistant to blending, in part due to the length of thepolymer chains which hinders the intimate intermingling of individualmolecules. Furthermore, physical blending is costly, requiring energy toheat the polymer components and to co-extrude the components through adie and sometimes lead to polymer degradation and property changes.

It is an object of the present invention to overcome the above problemsassociated with the physical blending of isotactic and syndiotacticpolyolefins. Accordingly, the present invention provides a catalystsystem for producing a polyolefin blend, which catalyst system comprisesa mixture including the following catalyst components:

-   (i) a catalyst component A capable of producing an isotactic olefin    polymer, and/or a catalyst component A′ capable of producing a    polymer comprising an isotactic polyolefin stereoblock; and-   (ii) a catalyst component B capable of producing a syndiotactic    polyolefin, and/or a catalyst component B′ capable of producing a    polymer comprising a syndiotactic polyolefin stereoblock;    wherein each of the components in the catalyst system is distinct    from the other components in the catalyst system.

In the context of the present invention, catalysts of type A and B meancatalysts capable of producing substantially homopolymeric isotacticpolyolefin and substantially homopolymeric syndiotactic polyolefinrespectively. Catalysts of type A′ and B′ mean catalysts capable ofproducing block co-polymers of light olefins which comprisepredominantly isotactic polyolefin blocks or predominantly syndiotacticpolyolefin blocks respectively. The further blocks in the blockco-polymers are not especially limited and may be blocks formed fromolefin monomers, or blocks formed from other monomers.

The catalyst system of the present invention comprises at least twodifferent catalyst components, one component of type A (and/or A′) andone component of type B (and/or B′). Thus, the present catalyst systemmay comprise any of the following component combinations:

-   -   A+B    -   A+B′    -   A′+B    -   A′+B′    -   A+B+A′    -   A+B+B′    -   A+B′+A′    -   A+B+B′; and    -   A+A′+B+B′        as well as further catalyst components, if desired.

In the case where a catalyst component is capable of producing an olefinpolymer comprising both isotactic and syndiotactic blocks, then thiscatalyst component is simultaneously of component type A′ and componenttype B′ and in the present context is termed an A′B′ component. However,for the avoidance of doubt, the present system cannot comprise one A′B′component alone, since the component of type (i) should be a differentcatalyst from the component of type (ii) in order that the catalystsystem is capable of producing at least two substantially differentpolyolefins. However, the present catalyst system may comprise twodifferent A′B′ components.

The present invention further provides a method for producing a blend ofan isotactic polyolefin and a syndiotactic polyolefin, which methodcomprises polymerising an olefin monomer in the presence of a catalystsystem as defined above.

The use of a catalyst mixture to produce an in situ mixture of isotacticpolyolefin and syndiotactic polyolefin (a chemical blending process)leads to polymer blends (chemical blends) that are much more homogeneousthan known blends produced by a physical blending process. The improvedhomogeneity of the present blends contributes to their improved physicaland mechanical properties.

Thus, the polymer blends produced by the catalyst system of the presentinvention have improved processibility and solidification properties ininjection blow moulding and injection moulding, whilst simultaneouslyshowing high transparency and flexibility. Fibres formed from thepresent blends have improved softness and improved thermal bondingcharacteristics. Films produced from the present blends have a reducedmodulus, being less stiff and have improved heat shrink, tear resistanceand impact resistance characteristics.

Typically, in the present catalyst system catalysts components (i) and(ii) are metallocene compounds. However, the catalyst components (i) and(ii) used in the present catalyst system for producing the iPP/sPP blendare not particularly limited, provided that they can be mixed with eachother.

In a preferred embodiment of the present invention, the catalystcomponent (i) comprises a catalyst A having the following formula:R″(CpR¹R²)(Cp′R′_(n))MQ₂wherein Cp is a substituted cyclopentadienyl ring; Cp′ is a substitutedor unsubstituted fluorenyl ring; R″ is a structural bridge impartingstereorigidity to the component; R¹ is a substituent on thecyclopentadienyl ring which is distal to the bridge, which distalsubstituent comprises a bulky group of the formula XR*₃ in which X is anatom from group IVA and each R* is the same or different and is chosenfrom a hydrogen or a hydrocarbyl group having from 1-20 carbon atoms, R²is a substituent on the cyclopentadienyl ring which is proximal to thebridge and positioned non-vicinal to the distal substituent and is ahydrogen or is of the formula YR#₃ in which Y is an atom from group IVA,and each R# is the same or different and is chosen from a hydrogen or ahydrocarbyl group having from 1-7 carbon atoms, each R′ is the same ordifferent and is a hydrocarbyl group having from 1-20 carbon atoms, andn is an integer of from 0-8; M is a metal atom from group IVB or isvanadium; and each Q is a hydrocarbon having from 1-20 carbon atoms oris a halogen;and/or a catalyst A having the following formulae:(Ind)2R′MQ2or;(IndH₄)₂R″MQ₂wherein each Ind is the same or different and is a substituted orunsubstituted indenyl group, wherein each IndH₄ is the same or differentand is a substituted or unsubstituted tetrahydroindenyl group, R′ is astructural bridge imparting stereorigidity to the component, R″ is astructural bridge imparting stereorigidity to the component; M is ametal atom from group IVB or is vanadium; and each Q is a hydrocarbonhaving from 1-20 carbon atoms or is a halogen. Preferably the structuralbridge comprises a C₁-C₄ alkylene group.

In common with catalyst A, the catalyst B used in component (ii) of thepresent catalyst system for producing the syndiotactic polyolefin is notparticularly limited, provided that it can be mixed with catalystcomponent (i). It is preferred in the present invention that thecatalyst B is a catalyst having the following formula:R″(CpR_(m))(Cp′R′_(r))MQ₂wherein Cp is a substituted or unsubstituted cyclopentadienyl ring; Cp′is a substituted or unsubstituted fluorenyl ring; R″ is a structuralbridge imparting stereorigidity to the component; each R is the same ordifferent and is a hydrocarbyl group having from 1-20 carbon atoms; eachR′ is the same or different and is a hydrocarbyl group having from 1-20carbon atoms; m is an integer of from 0-4; r is an integer from 0-8; Mis a metal atom from group IVB or is vanadium; and each Q is ahydrocarbon having from 1-20 carbon atoms or is a halogen. Preferablythe CpR_(m) group possesses bilateral symmetry and more preferably isunsubstituted (m=0).

Preferred catalysts of type A′ are those having the following formula.R″(CpR_(x))(Cp′R′_(y))MQ₂wherein Cp is a substituted cyclopentadienyl ring; Cp′ is a substitutedor unsubstituted fluorenyl ring; R″ is a structural bridge impartingstereorigidity to the component; each R is the same or different and isa hydrocarbyl group having from 1-20 carbon atoms, each R′ is the sameor different and is a hydrocarbyl group having from 1-20 carbon atoms,and x and y are independently an integer of from 0-4 and 0-8respectively; M is a metal atom from group IVB or is vanadium; and eachQ is a hydrocarbon having from 1-20 carbon atoms or is a halogen;wherein the CpR_(x) group lacks bilateral symmetry. In a preferredembodiment, the Cp group is substituted at the 3-position. Particularlypreferably the substituent comprises a trimethylsilyl group.

Preferred catalysts of type B′ are those having the following formula:R″(CpR_(q))XMQwherein Cp is a substituted or unsubstituted cyclopentadienyl ring or asubstituted or unsubstituted fluorenyl ring; R″ is a structural bridgebetween Cp and X imparting stereorigidity to the component; each R isthe same or different and is selected from a hydrocarbyl group havingfrom 1-20 carbon atoms, a halogen, an alkoxy group, an alkoxyalkylgroup, an alkylamino group or an alkylsilylo group; when Cp is acyclopentadienyl ring; q is an integer from 0-4; and when Cp is afluorenyl ring q is an integer from 0-8; X is a heteroatom from group VAor group VIA; M is a metal atom from group IIIB, IVB, VB or VIB in anyof its theoretical oxidation states; and each Q is a hydrocarbon havingfrom 1-20 carbon atoms or is a halogen; wherein the bilateral symmetryof the CpR_(q) group is maintained. Thus, preferably the CpR_(q) groupis symmetrically substituted.

The substituent or substituents present on the cyclopentadiene, indeneand fluorine rings in the above-described catalysts are not particularlylimited. The above rings, when comprising more than one substituent, maybe substituted with the same substituent throughout, or with differentsubstituents. Typically the substituents are independently selected froman aryl group and a hydrocarbyl group having from 1-20 carbon atoms. Themost preferred substituents are methyl groups. Other preferredsubstituents include Et, n-Pr, i-Pr, n-Bu, t-Bu, Me₃Si, R-O, cycloalkyl,and halogen.

The type of bridge present between the rings in the above-describedcatalysts is not itself particularly limited. Typically R″ comprises analkylidene group having 1 to 20 carbon atoms, a germanium group (e.g. adialkyl germanium group), a silicon group (e.g. a dialkyl silicongroup), a siloxane group (e.g. a dialkyl siloxane group), an alkylphosphine group or an amine group. Preferably, the substituent comprisesa silyl radical or a hydrocarbyl radical having at least one carbon atomto form the bridge, such as a substituted or unsubstituted ethylenylradical (e.g. —CH₂CH₂—). Most preferably R″ is isopropylidene (Me₂C),Ph₂C, ethylenyl, or Me₂Si. It is particularly preferred that catalystcomponents comprising a bisindenyl moiety comprise an ethylenyl or anMe₂Si bridge, whilst catalyst components comprising acyclopentadienyl-fluorenyl moiety comprise an Me₂C, Ph₂C, or Me₂Sibridge.

Some specific examples of preferred catalysts according to the presentinvention are the following:

A (iPP Catalysts):

-   -   Me₂Si(2-Me-Benz-Ind)₂ ZrCl₂    -   Me₂Si(2-Me-4-Naphthyl-Ind)₂ ZrCl₂    -   Me₂Si(2-Me-Ind)₂ ZrCl₂    -   Ph₂C(t-BuCp)(Flu) ZrCl₂    -   Et(Ind)₂ ZrCl₂    -   Et(IndH₄)₂ ZrCl₂    -   Me₂Si(2-Me-4,5Benzyl-Ind)₂ ZrCl₂    -   (R1R2Cp-Flu)RZrCl2

A′ (iPP Block Catalysts)

-   -   Ph₂C(3-Me₃Si-Cp)(Flu) ZrCl₂

B (sPP Catalysts)

-   -   Ph₂C(Cp)(Flu) ZrCl₂

B′ (sPP Block Catalysts)

-   -   Me₂S(t-BuN)(2,7-di-t-Bu-Flu) ZrCl₂

The catalyst components (i) and (ii) of the present catalyst system canbe mixed by a physical process (physical blending), such as by slurryinga powdered form of the catalysts together in a hydrocarbon solvent.Alternatively components (i) and (ii) can be mixed by a chemical process(chemical blending). Chemical blending can be effected by, for example,forming a solution containing both catalysts (i) and (ii) and adding thesolution to the support. It is preferred that chemical blending iscarried out by immobilising both catalyst (i) and catalyst (ii) on asolid support in such a manner that one or more individual particles ofthe solid support have both catalyst (i) and catalyst (ii) immobilisedon them.

The proportion of catalyst (i) to catalyst (ii) in the present catalystsystem is not especially limited, and depends on the ratio of isotacticto syndiotactic polymer required in the final product. This will bedependent on the particular application for which the product is to beused. Typically, the proportion of catalyst (i) to catalyst (ii) is suchthat the final isotactic/syndiotactic blend comprises 50 wt. % or moreisotactic polyolefin and from 0.5-50 wt. % of syndiotactic polyolefin.More preferably, the final blend comprises from 0.3-15 wt. % ofsyndiotactic polyolefin and most preferably from 1-10 wt. % ofsyndiotactic polyolefin.

In order to produce polyolefin blends displaying an especially highdegree of homogeneity (and consequently especially favourableproperties) it is preferred that the present catalyst system comprises acatalyst component capable of producing a polyolefin comprising bothisotactic polyolefin blocks and syndiotactic or atactic polyolefinblocks (an A′ catalyst), or a catalyst capable of producing a polyolefincomprising both syndiotactic polyolefin blocks and isotactic or atacticpolyolefin blocks (a B′ catalyst). In the context of the presentinvention, these catalysts are termed stereoblock catalysts. Preferredcatalyst components of this type are those capable of producing apolyolefin comprising both isotactic and syndiotactic polyolefin blocks(i.e. A′B′ catalyst components). It is particularly preferred that thepresent catalyst system comprises an A component, a B component and anA′B′ component.

Without being bound by theory, it is believed that, since thepolyolefins produced by the stereoblock catalysts comprise bothisotactic and syndiotactic units, they mix more readily with isotacticand syndiotactic homopolymers than these homopolymers do with eachother. Thus, the inclusion of one or more stereoblock catalysts in thepresent catalyst system improves miscibility, i.e. it ensures that thepolyolefin blend produced comprises a polymer that promotes mixingbetween the isotactic and syndiotactic polyolefins. The resultingpolymer blend is thus more homogeneous than would otherwise be the case.Consequently the polymer has fewer weak spots in the crystal structure,leading to significant improvements in its mechanical strength.

In addition to the above catalyst components (i) and (ii), the catalystsystem of the present invention may comprise one or more co-catalystscapable of activating any one or more of the catalyst components.Typically, the co-catalyst comprises an aluminium- or boron-containingco-catalyst.

Suitable aluminium-containing co-catalysts comprise an alumoxane, analkyl aluminium compound and/or a Lewis acid.

The alumoxanes that can be used in the present invention are well knownand preferably comprise oligomeric linear and/or cyclic alkyl alumoxanesrepresented by the formula (I):

for oligomeric linear alumoxanes; and formula (II)

for oligomeric cyclic alumoxanes,wherein n is 1-40, preferably 10-20; m is 3-40, preferably 3-20; and Ris a C₁-C₁-C₈ alkyl group, preferably methyl. Generally, in thepreparation of alumoxanes from, for example, aluminium trimethyl andwater, a mixture of linear and cyclic compounds is obtained.

Suitable boron-containing co-catalysts may comprise a triphenylcarbeniumboronate, such as tetrakis-pentafluorophenyl-borato-triphenylcarbeniumas described in EP-A-0427696:

or those of the general formula below, as described in EP-A-0277004(page 6, line 30 to page 7, line 7):

The catalyst system of the present invention may be employed in anymethod, provided that the required catalytic activity is not impaired.In a preferred embodiment of the present invention, the catalyst systemis employed in a solution polymerisation process, which is homogeneous,or a slurry process, which is heterogeneous. In a solution process,typical solvents include hydrocarbons having 4-7 carbon atoms such asheptane, toluene or cyclohexane. In a slurry process it is necessary toimmobilise the catalyst system on an inert support, particularly aporous solid support such as talc, inorganic oxides and resinous supportmaterials such as polyolefin. Preferably, the support material is aninorganic oxide in its finely divided form.

Suitable inorganic oxide materials which are desirably employed inaccordance with this invention include group IIA, IIIA, IVA, or IVBmetal oxides such as silica, alumina and mixtures thereof. Otherinorganic oxides that may be employed either alone or in combinationwith the silica, or alumina are magnesia, titania, zirconia, and thelike. Other suitable support materials, however, can be employed, forexample, finely divided functionalised polyolefins such as finelydivided polyethylene.

Preferably, the support is a silica support having a surface area offrom 200-700 m²/g and a pore volume of from 0.5-3 ml/g.

The amount of alumoxane and metallocenes usefully employed in thepreparation of the solid support catalyst can vary over a wide range.Preferably the aluminium to transition metal mole ratio is in the range1:1 to 130:1, preferably 1:1 to 100:1, more preferably 5:1 to 70:1 andmost preferably 5:1 to 50:1.

The order of addition of the catalyst components and alumoxane to thesupport material can vary. In accordance with a preferred embodiment ofthe present invention alumoxane dissolved in a suitable inerthydrocarbon solvent is added to the support material slurried in thesame or other suitable hydrocarbon liquid and thereafter a mixture ofthe catalyst components is added to the slurry.

Preferred solvents include mineral oils and the various hydrocarbonswhich are liquid at reaction temperature and which do not react with theindividual ingredients. Illustrative examples of the useful solventsinclude the alkanes such as pentane, iso-pentane, hexane, heptane,octane and nonane; cycloalkanes such as cyclopentane and cyclohexane,and aromatics such as benzene, toluene, ethylbenzene and diethylbenzene.

Preferably the support material is slurried in toluene and the catalystcomponents and alumoxane are dissolved in toluene prior to addition tothe support material.

The polyolefins that catalysts (i) and (ii) are capable of producing arenot particularly limited, except that the monomeric olefin unit formingeach polyolefin must have three or more carbon atoms. It is particularlypreferred that both of catalyst components (i) and (ii) are capable ofproducing polypropylene.

The catalyst system of the present invention is used in the method ofthe present invention to produce blends of isotactic polyolefin andsyndiotactic polyolefin. It is especially preferred that the method ofthe present invention is a method of producing a blend of isotacticpolypropylene and syndiotactic polypropylene (an iPP/sPP blend).

The conditions employed for polymerisation in the method of the presentinvention are not particularly limited, provided they are sufficient toeffectively polymerise the particular monomeric olefin used as astarting material. Typical polymerisation conditions in a slurrypolymerisation are at a temperature of from 20-120° C., a pressure offrom 0.1-5.6 MPa and a reaction time of from 10 mins to 4 hours.

The polyolefin blends of the present invention, and in particular theiPP/sPP, blends may be used to produce fibres. For the production ofspunlaid iPP/sPP fibres, a typical extrusion temperature is in the rangeof from 200-260° C., most typically from 230-250° C. For the productionof staple fibres, a typical extrusion temperature would be in the rangeof from 230-330° C., most typically from 280-300° C.

Fibres produced in accordance with the present invention may be producedfrom iPP/sPP blends having other additives to improve the mechanicalprocessing or spinnability of the fibres. The fibres may be used toproduce non-woven fabrics for use in filtration; in personal careproducts such as wipers, diapers, feminine hygiene products andincontinence products; in medical products such as wound dressings,surgical gowns, bandages and surgical drapes; in protective covers; inoutdoor fabrics and in geotextiles. Non-woven fabrics made with iPP/sPPfibres can be part of such products, or constitute entirely theproducts. As well as making non-woven fabrics, the fibres may also beemployed to make a woven knitted fabric or mat. The non-woven fabricsproduced from the fibres in accordance with the invention can beproduced by several processes, such as air through blowing, meltblowing, spun bonding or bonded carded processes. The fibres may also beformed as a non-woven spunlace product which is formed without thermalbonding by fibres being entangled together to form a fabric by theapplication of a high pressure fluid such as air or water.

The invention will now be described in further detail by way of exampleonly, with reference to the following specific embodiments.

EXAMPLES

Catalysts of type A (iPP) were prepared in accordance with F. Wild, L.Zsolnai, G. Hutter and H. H. Brintzinger, J. Organomet. Chem., 232, 233,1982. Catalysts of type A′ (iPP/sPP) were prepared in accordance with A.Razavi, “Presentation to International Business Forum on SpecialityPolyolefins” Sep. 22-24, 1992. Catalysts of type B (sPP) were preparedin accordance with the method of Razavi and Ferrara as published in theJ. Organomet. Chem., 435, 299, 1992.

Example 1

Catalyst Preparation

(Me₂Si)(2-Me-4,5-Benzyl-Ind)₂ZrCl₂ (a catalyst A) and(Ph₂C)(Cp)(Flu)ZrCl₂ (a catalyst B) were prepared.

Catalyst A Preparation—Two Steps Procedure

The support used was silica having a total pore volume of 4.22 ml/g anda surface area of 322 m²/g. This silica was dried in a fluidised bedreactor (for 6 hours at 150° C. with 75 Nl of H₂) to remove thephysically absorbed water.

5 g of this dried silica were suspended in 100 ml of dried toluene in around bottom flask equipped with a magnetic stirrer, a nitrogen inletand a dropping funnel. A 30wt % MAO solution in toluene (0.7-1.3 weightequivalents of MAO to silica, preferably 0.9 weight equivalents) wasadded dropwise to the silica suspension at room temperature. A reactionbetween MAO and the hydroxyl groups of the silica occurred, and theexothermic reaction (10° C. temperature rise) was accompanied by methanegas release. The slurry was heated to 110° C. and allowed to react for 4hours at toluene reflux. The suspension was then filtered on a fritfunnel. The reaction product was washed until the filtrate wassubstantially free of MAO. After the washing with toluene, theprecipitate was then washed with pentane to facilitate drying. Thesupport was finally dried under a mild vacuum. 9.7 g of support wasobtained as a white powder.

To produce the activated catalyst, the metallocene(Me₂Si)(2-Me-4,5-Benzyl-Ind)₂ZrCl₂ (2 to 6 wt % of metallocene loadingon the final catalyst, preferably 4 wt %) was dissolved in toluene andadded to the toluene suspended reaction product of silica and MAO atroom temperature. Reaction was allowed to take place for 2 hours at roomtemperature to form the active sites by reaction of the remainingaluminium alkyl functions on the support with the metallocene. Thesuspension was filtered and washed with toluene until filtrate wascolourless. The precipitate was then washed with pentane to facilitatedrying and finally dried under mild vacuum.

Catalyst B Preparation—One Pot Procedure.

The support used was silica having a total pore volume of 4.22 ml/g anda surface area of 322 m²/g. This silica was dried in a fluidised bedreactor (for 6 hours at 150° C. with 75 Nl of H₂) to remove thephysically absorbed water.

5 g of this dried silica were suspended in 100 ml of dried toluene in around bottom flask equipped with a magnetic stirrer, a nitrogen inletand a dropping funnel. In this procedure, the ion pair was formed byinitial reaction of MAO solution with the metallocene(Ph₂C)(CP)(Flu)ZrCl₂ (2 to 6 wt % of metallocene to final catalyst,preferably 6 wt %). The ion pair solution was then added to thesilica/toluene suspension (0.7-1.3 weight equivalents of MAO to silica,preferably 0.9 wt equivalents). The suspension was allowed to react for4 hours at toluene reflux. The resulting slurry was filtered and washedwith toluene and pentane and finally dried under mild vacuum.

Physical Blends of Catalysts Preparation

To produce a physical blend of supported catalysts, powder of eachsupported metallocene catalyst was mixed to produced 75:25, 83:17 and90:10 physical blends of catalyst A:catalyst B. In each case, thecatalyst system comprised a 6 wt.% loading of metallocene.

Example 2

Catalyst Preparation

(Me₂Si)(2-Me-Ind)₂ZrCl₂ (a catalyst A) and (Ph₂C)(Cp)(Flu)ZrCl₂ (acatalyst B) were prepared.

Catalyst A Preparation—Two Steps Procedure

The catalyst system was prepared according to the two steps proceduredescribed above in Example 1.

Catalyst B Preparation—One Pot Procedure

The catalyst system was prepared according to the one pot proceduredescribed above in Example 1.

Physical Blends of Catalysts Preparation

A physical blend of supported catalysts was produced by mixing powder ofeach supported metallocene catalyst to produce a 72:25 physical blend ofcatalyst A:catalyst B. In each case, the catalyst system comprised a 6wt. % loading of metallocene.

Example 3

Catalyst Preparation—Two Steps Procedure

(Ph₂C)((Me₃Si)Cp)(Flu)ZrCl₂ (a catalyst A′) and (Ph₂C)(Cp)(Flu)ZrCl₂ (acatalyst B) were prepared.

The support used was silica having a total pore volume of 4.22 ml/g anda surface area of 322 m²/g. This silica was dried in a fluidised bedreactor (for 6 hours at 150° C. with 75 Nl of H₂) to remove thephysically absorbed water.

5 g of this dried silica were suspended in 100 ml of dried toluene in around bottom flask equipped with a magnetic stirrer, a nitrogen inletand a dropping funnel. A 30 wt. % MAO solution in toluene (0.7-1.3weight equivalents of MAO to silica, preferably 0.9 weight equivalents)was added dropwise to the silica suspension at room temperature. Areaction between MAO and the hydroxyl groups of the silica occurred, andthe exothermic reaction (10° C. temperature rise) was accompanied bymethane gas release. The slurry was heated to 110° C. and allowed toreact for 4 hours at toluene reflux. The suspension was then filtered ona frit funnel. The reaction product was washed until the filtrate wassubstantially free of MAO. After the washing with toluene, theprecipitate was then washed with pentane to facilitate drying. Thesupport was finally dried under a mild vacuum. 9.7 g of support wasobtained as a white powder.

To produce the activated catalyst, the metallocenes(Ph₂C)((Me₃Si)Cp)(Flu)ZrCl₂ and (Ph₂C)(Cp)(Flu)ZrCl₂ were dissolved intoluene and added to toluene suspended reaction product of silica andMAO at room temperature. Reaction was allowed to take place for 2 hoursat room temperature to form the active sites by reaction of theremaining aluminium alkyl functions on the support with the metallocene.The suspension was filtered and washed with toluene until filtrate wascolourless. The precipitate was then washed with pentane to facilitatedrying and finally dried under mild vacuum to produce an 80:20 (byweight) chemical blend of catalyst A′:catalyst B. This procedure wasrepeated to produce 90:10 and 95:5 chemical blends of A′:B. The totalloading of metallocenes was 6 wt.%.

Polymerisation of Propylene

Each of the above catalyst systems, as well as systems comprising onlythe individual catalyst components, were used to polymerise propylene. 2litres of liquid propylene were polymerised using 100 mg of eachcatalyst.

Example 1

Table 1 below shows the results of microtacticity analysis from ¹³C NMRdata in which the percent of mmmm pentads decreases as the content ofBenzyl-Ind catalyst in the catalyst system decreases.

TABLE 1 Catalysts of Example 1 Catalyst Wt. % sPP % mmmm % rrrr % m % riPP and sPP catalysts alone Benzyl-Ind (iPP) — 93.7 0.37 97.4 2.6 Cp(sPP) — 2.4 75.4 10.2 89.8 Physical blends of iPP and sPP catalystsBenzyl-Ind/Cp; 28.3 69.3 19.2 74.9 25.1 75/25 Benzyl-Ind/Cp; 21.7 76.313.2 81.5 18.5 83/17 Benzyl-Ind/Cp; 7.5 87.6 3.7 92.5 7.5 90/10

Example 2

Table 2 below shows the results of microtacticity analysis from ¹³C NMRdata in which the percent of mmmm pentads decreases as the content ofMe-Ind catalyst in the catalyst system decreases.

TABLE 2 Catalysts of Example 2 Catalyst Wt. % sPP % mmmm % rrrr % m % riPP and sPP catalysts alone Me-Ind (iPP) — 93.4 0.0 97.4 2.3 Cp (sPP) —2.4 75.4 10.2 89.8 Physical blend of iPP and sPP catalysts Me-Ind/Cp;75/25 — 78.4 12.3 83.4 16.6

Example 3

Table 3 below shows the results of microtacticity analysis from ¹³C NMRdata in which, for both the chemically and physically blended catalystsystems, the percent of mmmm pentads increases as the content of TMSCpcatalyst in the catalyst system increases.

TABLE 3 Wt. % iPP Catalyst in sPP % mmmm % rrrr % m % r iPP/sPP and sPPcatalysts alone TMSCp — 53.8 17.5 69.9 30.1 (iPP/sPP) Cp (sPP) — 2.475.4 10.2 89.8 Physical blends of iPP/sPP and sPP catalysts TMSCp/Cp;1.0 3.0 75.0 10.8 89.2 50/50 TMSCp/Cp; 8.5 6.8 70.5 15.2 84.8 75/25TMSCp/Cp; 22.3 13.9 63.1 23.5 76.5 90/10 Chemical blends of iPP/sPP andsPP catalysts TMSCp/Cp; 5.0 4.3 72.6 13.2 86.8 80/20 TMSCp/Cp; 20.0 11.963.6 22.2 77.8 90/10 TMSCp/Cp; 95/5 30.0 17.5 57.7 28.1 71.9

1. A catalyst system for producing a polyolefin blend, which catalystsystem comprises a mixture of a first catalyst component supported on afirst support and a second catalyst component supported on a secondsupport, wherein the first catalyst component is at least one of acatalyst component A capable of producing an isotactic olefin polymer,and a catalyst component A′ capable of producing a polymer comprising anisotactic polyolefin block; and the second catalyst component is atleast one of a catalyst component B capable of producing an syndiotactiepolyolefin, and a catalyst component B′ capable of producing a polymercomprising an syndiotactic polyolefin block; wherein each of thecomponents in the catalyst system is distinct from the other componentsin the catalyst system, and wherein the catalyst component A comprisesat least one metallocene having the formula:R″(CpR¹R²)(Cp′R′n)MQ₂  (1) wherein: (CpR¹R²) is a substitutedcyclopentadienyl ring; (Cp′R′n) is a substituted or unsubstitutedfluorenyl ring; R″ is a structural bridge imparting stereorigidity tothe component; R¹ is a substituent on the cyclopentadienyl ring which isdistal to the bridge, which distal substituent comprises a bulky groupof the formula XR*₃ in which X is an atom from group IVA and each R* isthe same or different and is chosen from a hydrogen or a hydrocarbylgroup having from 1-20 carbon atoms, R² is a substituent on thecyclopentadienyl ring which is proximal to the bridge and positionednon-vicinal to the distal substituent and is a hydrogen or is of theformula YR#₃ in which Y is an atom from group IVA, and each R# is thesame or different and is chosen from a hydrogen or a hydrocarbyl grouphaving from 1-7 carbon atoms, each R′ is the same or different and is ahydrocarbyl group having from 1-20 carbon atoms, and n is an integer offrom 0-8; M is a metal atom from group IVB or is vanadium; and each Q isa hydrocarbon having from 1-20 carbon atoms or is a halogen; or theformula:(Ind)₂R′MQ₂  (2) or the formula:(IndH₄)₂R″MQ₂  (3) wherein: each Ind is the same or different and is asubstituted or unsubstituted indenyl group, wherein each IndH₄ is thesame or different and is a substituted or unsubstitutedtetrahydroindenyl group, R′ is a structural bridge impartingstereorigidity to the component, R″ is a structural bridge impartingstereorigidity to the component; M is a metal atom from group IVB or isvanadium; and each Q is a hydrocarbon having from 1-20 carbon atoms oris a halogen, wherein the catalyst component B has the formula:R″(CpR_(m))(Cp′R′_(r))MQ₂  (4) wherein: (CpR_(m)) is a substituted orunsubstituted cyclopentadienyl ring; (Cp′R′_(r)) is a substituted orunsubstituted fluorenyl ring; R″ is a structural bridge impartingstereorigidity to the component, each R is the same or different and isa hydrocarbyl group having from 1-20 carbon atoms; each R′ is the sameor different and is a hydrocarbyl group having from 1-20 carbon atoms; mis an integer of from 0-4; r is an integer from 0-8; M is a metal atomfrom group IVB or is vanadium; and each Q is a hydrocarbon having from1-20 carbon atoms or is a halogen, wherein the catalyst component A′ hasthe formula:R″(CpR_(x))(Cp′R′y)MQ₂  (5) wherein: (CpR_(x)) is a substitutedcyclopentadienyl ring; (Cp′R′y) is a substituted or unsubstitutedfluorenyl ring; R″ is a structural bridge imparting stereorigidity tothe component; each R is the same or different and is a hydrocarbylgroup having from 1-20 carbon atoms, each R′ is the same or differentand is a hydrocarbyl group having from 1-20 carbon atoms and x and y areindependently an integer of from 1-4 and 0-8 respectively; M is a metalatom from group IVB or is vanadium; and each Q is a hydrocarbon havingfrom 1-20 carbon atoms or is a halogen; wherein the CpR_(x) group lackbilateral symmetry, and wherein the catalyst component B′ has theformula:R″(CpR_(q))XMQ₂  (6) wherein: CpR_(q) is a substituted cyclopentadienylring or a substituted or unsubstituted fluorenyl ring; R″ is astructural bridge between Cp and X imparting stereorigidity to thecomponent; each R is the same or different and is selected from ahydrocarbyl group having from 1-20 carbon atoms, a halogen, an alkoxygroup, and alkoxyalkyl group, an alkoxyalkyl group, an alkkylamino groupor an alkylsilylo group when Cp is a cyclopentadienyl ring, q is aninteger from 0-4; and when Cp is a fluorenyl ring q is an integer from0-8; X is a heteroatom from group VA or group VIA; M is a metal atomfrom group IIIB, IVB, VB or VIB in any of its theoretical oxidationstates; and each Q is a hydrocarbon having from 1-20 carbon atoms or isa halogen; wherein the bilateral symmetry of the CpR_(q) group ismaintained.
 2. A catalyst system according to claim 1, wherein M is Ti,Zr, or Hf.
 3. A catalyst system according to claim 2, wherein Q is Cl.4. A catalyst system according to claim 1, wherein R″ is substituted orunsubstituted and comprises an alkylene radical having from 1-20 carbonatoms, a dialkyl germanium group, a dialkyl silicon group, a dialkylsiloxane group, an alkyl phosphine radical or an amine radical.
 5. Acatalyst system according to claim 4, wherein R″ comprises anisopropylidene, (Me₂C), Ph₂C, ethylenyl or Me₂Si group.
 6. A catalystsystem according to claim 1, further comprising an aluminum- orboron-containing activating agent capable of activating at least one ofsaid first catalyst component and said second catalyst component.
 7. Acatalyst system according to claim 1, wherein catalyst component A iscapable of producing isotactie polypropylene and catalyst component B iscapable of producing syndiotactie polypropylene.
 8. A catalyst systemaccording to claim 1 wherein the first catalyst component comprises acatalyst component A as defined by formula (1) wherein R¹ is asubstituent on the cyclopentadienyl ring Cp, at a position which isdistal to the bridge R″ and R² is a substituent on the cyclopentadienylring Cp, at a position which is proximal to the bridge R″ and ispositioned non-vicinal to the distal substituent R¹.
 9. A catalystsystem according to claim 1, wherein the first catalyst component is ametallocene according to formula (2) or (3), in which R″ is a C₁-C₄alkylene group.
 10. A catalyst system according to claim 1, wherein thesecond catalyst component is a catalyst component B according to formula(4), in which the group CpR_(m) has bilateral symmetry.
 11. A catalystsystem according to claim 10 in which the value of m is 0 to providethat the group CpR_(m) is unsubstituted.
 12. A catalyst system accordingto claim 1, wherein the first catalyst component comprises a catalystcomponent A′ as characterized by formula (5) in which the group CpR_(x)lacks bilateral symmetry.
 13. A catalyst system according to claim 12wherein the group CpR_(x) is substituted at the 3 position.
 14. Acatalyst system according to claim 13 wherein the substituent K is atrimethylsilyl group.
 15. A catalyst system according to claim 1,wherein the second catalyst component comprises a catalyst component Bas characterized by formula (6), in which the group CpR_(q) is asymmetrically substituted cyclopentadienyl group or fluorenyl group. 16.A process for producing a blend of an isotactic polyolefin and asyndiotactie polyolefin, which comprises: a. providing a catalyst systemfor producing a polyolefin blend, which catalyst system comprises amixture of a first catalyst component supported on a first support and asecond catalyst component supported on a second support, wherein thefirst catalyst component is s at least one of a catalyst component Acapable of producing an isotactie olefin polymer, and a catalystcomponent A′ capable of producing a polymer comprising an isotacticpolyolefin block; and the second catalyst component is at least one of acatalyst component B capable of producing an syndiotactic polyolefin,and a catalyst component B′ capable of producing a polymer comprising ansyndiotactic polyolefin block; wherein each of the components in thecatalyst system is distinct from the other components in the catalystsystem, and wherein the catalyst component A comprises at least onemetallocene having the formula:R″(CpR′Rb(cp′R′n)MQ₂  (1) wherein: (CpR¹R²) is a substitutedcyclopentadienyl ring; (Cp′R′n) is a substituted or unsubstitutedfluorenyl ring; R″ is a structural bridge imparting stereorigidity tothe component; R¹ is a substituent on the cyclopentadienyl ring which isdistal to the bridge, which distal substituent comprises a bulky groupof the formula XR*₃ in which X is an atom from group IVA and each R* isthe same or different and is chosen from a hydrogen or a hydrocarbylgroup having from 1-20 carbon atoms, R² is a substituent on thecyclopentadienyl ring which is proximal to the bridge and positionednon-vicinal to the distal substituent and is a hydrogen or is of theformula YR#₃ in which Y is an atom from group IVA, and each R# is thesame or different and is chosen from a hydrogen or a hydrocarbyl grouphaving from 1-7 carbon atoms, each R′ is the same or different and is ahydrocarbyl group having from 1-20 carbon atoms, and n is an integer offrom 0-8; M is a metal atom from group IVB or is vanadium; and each Q isa hydrocarbon having from 1-20 carbon atoms or is a halogen; or theformula:(Ind)₂R′MQ₂  (2) or the formula:(IndH₄)₂R″MQ₂  (3) wherein: each md is the same or different and is asubstituted or unsubstituted indenyl group, wherein each IndU4 is thesame or different and is a substituted or unsubstitutedtetrahydroindenyl group, R′ is a structural bridge impartingstereorigidity to the component, R″ is a structural bridge impartingstercorigidity to the component; M is a metal atom from group IVB or isvanadium; and each Q is a hydrocarbon having from 1-20 carbon atoms oris a halogen, wherein the catalyst component B has the formula:R″(CPR_(m)(CP′R′) _(r))MQ₂  (4) wherein: (CpR_(m)) is a substituted orunsubstituted cyclopentadienyl ring; (Cp′R′_(r)) is a substituted orunsubstituted fluorenyl ring; R″ is a structural bridge impartingstereorigidity to the component, each R is the same or different and isa hydrocarbyl group having from 1-20 carbon atoms; each R′ is the sameor different and is a hydrocarbyl group having from 1-20 carbon atoms; mis an integer of from 0-4; r is an integer from 0-8; M is a metal atomfrom group IVB or is vanadium; and each Q is a hydrocarbon having from1-20 carbon atoms or is a halogen, wherein the catalyst component A′ hasthe formula:R″(CpR_(x))(Cp′R′y)MQ₂  (5) wherein: (CpR_(x)) is a substitutedcyclopentadienyl ring; (Cp′R′y) is a substituted or unsubstitutedfluorenyl ring; R″ is a structural bridge imparting stereorigidity tothe component; each R is the same or different and is a hydrocarbylgroup having from 1-20 carbon atoms, each R′ is the same or differentand is a hydrocarbyl group having from 1-20 carbon atoms and x and y areindependently an integer of from 1-4 and 0-8 respectively; M is a metalatom from group IVB or is vanadium; and each Q is a hydrocarbon havingfrom 1-20 carbon atoms or is a halogen; wherein the CpR_(x) group lackbilateral symmetry, and wherein the catalyst component B′ has theformula:R″(CpR_(q))XMQ₂  (6) wherein: CpRq is a substituted cyclopentadienylring or a substituted or unsubstituted fluorenyl ring; R″ is astructural bridge between Cp and X imparting stercorigidity to thecomponent; each R is the same or different and is selected from ahydrocarbyl group having from 1-20 carbon atoms, an alkoxyalkyl group,an alkylamino group or an alkylsilylo group; from 0-4; and when Cp is afluorenyl ring q is an integer from 0-8; X is a heteroatom from group VAor group VJA; M is a metal atom from group IIIB, IVB, VB or VIB in anyof its theoretical oxidation states; and each Q is a hydrocarbon havingfrom 1-20 carbon atoms or is a halogen; wherein the bilateral symmetryof the CpRq group is maintained; and further comprising a co-catalyst ofan aluminum- or boron-containing activating agent capable of activatingat least one of said first catalyst component and said second catalystcomponent; b. contacting said catalyst system with an olefin monomer ina polymerization reaction zone under polymerization conditions to form apolyolefin product; and c. withdrawing said polyolefin product from saidpolymerization reaction zone.
 17. The process of claim 16 wherein saidolefin monomer is propylene.
 18. The process of claim 17 wherein saidfirst catalyst component is a catalyst component effective in thepolymerization of propylene to produce isotactic polypropylene and saidsecond catalyst component is a catalyst component effective in thepolymerization of propylene to produce syndiotactic polypropylene,wherein the polyolcfm product withdrawn from said polymerizationreaction zone is a mixture of isotactic polypropylene and syndiotacticpolypropylene.